A wave of anti-Trump, pro-climate enthusiasm has washed across the US since president Donald Trump decided to abandon the Paris climate agreement.

Affirmations of the Paris goals have come from thousands of centres of power. State capitols, mayors’ offices and boardrooms have aligned to tell Trump “We Are Still In”. Twelve states, plus Puerto Rico, representing a third of US citizens, have joined the United States Climate Alliance, which commits to meet the carbon cuts the US pledged to the Paris accord.

But those standing by the agreement had, until this week, universally ignored the part of the deal that binds it all together – cash.

The leaders of Germany, France and Italy recognised this in a joint statement released within hours of Trump’s announcement in which they reaffirmed their commitment to the deal “including its climate finance goals”.

But Paris-allies in the US have assiduously ignored this aspect. Even California governor Jerry Brown, lauded as the US’ new climate leader, was silent on cash when he responded to Trump’s Paris withdrawal this month.

On Monday, Seattle city council bucked that trend with official recognition that support for the UN Green Climate Fund (GCF) was part of the US’ responsibilities under the Paris deal.

Under the Paris Agreement, rich countries agreed to channel funds through the “Financial Mechanism”, a set of institutions including the GCF, to the developing world.

In 2015, the US pledged $3bn to the GCF. With only $1bn of that paid, Trump has now turned off the tap.

“Being in Paris means more than just mitigating your emissions,” says Benito Müller, the convenor of international climate policy research at Oxford University’s Environmental Change Institute. “We need to make sure it becomes common currency that finance is recognised as part of the Paris Agreement.”

Climate finance is important for two reasons.

Firstly, it supports emerging economies like China, India and South Africa – responsible for a growing share of global emissions – in shifting to a cleaner development pathway. If they can be encouraged to meet rampant energy demand from renewables instead of coal, it makes the climate safer for everyone.

Secondly, it goes to protect the poorest, who have done little to cause climate change, from its worst effects. Providing drought-resistant seeds and flood defences goes some way to making up for the damage inflicted by industrialisation.

“The impacts of climate change and the subsequent costs of avoiding it or protecting against it are going to fall more heavily on the poorest countries,” says Müller.

More than one billion people live in the 48 most climate-vulnerable countries. It’s hard to overstate the importance of climate finance – the catch-all term for this flow of cash – in those lands, where poverty multiplies the dangers of a warming world.

That’s why Seattle’s intervention is so important. While it comes with no details about the nature or quantity of “support” it pledges to the GCF, it recognises the aspect of the agreement that brought the developing world on board.

Industrialised nations have agreed to mobilise $100bn a year in climate finance from 2020 – a figure that some argue wildly underestimates the burden that warming places on the developing world.

“This is not just to feel good,” says Müller, maintaining trust and delivering on financial promises is in the self-interest of rich countries. If that number is not met in three years – and it already looked shaky before Trump’s announcement – poor countries may walk away from the deal. If they decide to fuel their development with coal, “that could swamp all our efforts” and the whole world would suffer the consequences, he said.

If the states and cities that have backed the Paris accord’s emissions cuts were to similarly back the Green Climate Fund, it would go some way to fill the Trump gap. But the GCF is often criticised for its behindhand start to life. It got $10bn worth of start-up pledges ($8bn after the US U-turn), but so far has only disbursed $5m. It’s not running out of money any time soon.

Müller argues that cities and states who want to fully embrace the Paris accord could do better than focus on the GCF. There are a range of institutions set up to process climate finance. In the developing world, the Special Climate Change Fund, the Least Developed Countries Fund and the Adaptation Fund have project pipelines waiting for money but are critically under-resourced.

States that have joined the United States Climate Alliance (dark) and others who have expressed support for the Paris accord (light) (Source: Thekiller160)

These small funds act as a “trust weather vane,” says Müller. He has been working since before the Paris agreement was struck to get sub-national governments to pitch into them. It is here, he said, that contributions made by cities and states – inevitably smaller than national sums – can make a real difference immediately.

At the Paris conference, the Canadian province of Quebec gave $6m to the Least Developed Countries Fund. In Massachusetts, legislation that will give taxpayers the option to send a portion of their tax rebates to the same body is now before the state senate.

Now, Trump’s anti-climate stance and recent withdrawal from the Paris accord has energised state governors and city officials, who see this as an issue from which they can stand apart from the president and legitimately claim to be leading the country.

Müller is hoping to harness that energy and ensure that it also washes into climate finance commitments. He has been in contact with the offices of the governors of California and New York, as well as leaders in Quebec and British Colombia.

The sums this constellation of US governments can raise from their payers of rates and taxes will, in all likelihood, come nowhere near filling the $2bn hole left by Trump. But a new flow of money, however symbolic, would speak of solidarity with the rest of the world and more truly reflect the Paris accord.